High-pressure and high-temperature test apparatus



Patented Oct. 4, 1949 v HIGH-PRESSURE AND HIGH-TEMPERATURE TESTAPPARATUS Percy W. Bridgman, Cambridge, Samuel S. Kistler,

West Boylston, and William Wheildon, Jr., Framingham, Mass., assignors,by direct and mesne assignments, to Norton Company, Worcester, Mass., acorporation of Massachusetts Application November 22, 1946, Serial No.711,572 6 Claims. (01. 73-154) The invention relates to methods andapparatus for heating and pressing.

One object of the invention is to provide a method for subjectingmaterial to a great pressure while heated. Another object of theinvention is to provide an apparatus for heating and pressingsimultaneously. Another object is to perform a series of chemicalreactions producing intense heat in a closed chamber under greatpressure. Another object is to provide an automatic detonating apparatusto detonate a charge responsive to subjecting the apparatus to greatpressure. Another object is to provide a charge which will react toproduce high temperatures under pressure of the order of many thousandsof atmospheres. Another object is rapidly to produce high temperatureunder great pressure. Another object is to provide reaction charges anda mechanism for starting the reactions under enormous pressure withoutthe use of any external connections so that the reactions can take placein a closed mold. Another object of the invention is to provide asatisfactory detonator to set ofi a charge under high pressure. Anotherobject of the invention is to provide a satisfactory igniter charge orstarter charge which will be ignited by the detonator and will set ofithe main charge under high pressure. Another object of the invention isto provide a main charge which will be set off by the igniter chargeunder conditions of great pressure. Another object is to provide adetonator and charges which will operate under great pressures and inwhich the charges will react substantially to completion under thesepressures. Another object is to provide an apparatus and method forgeophysical research. Other objects will be in part obvious or in partpointed out hereinafter.

The invention accordingly consists in the features of construction,combinations of elements, arrangements of parts, and in the severalsteps and relation and order of each of said steps, to one or more ofthe others thereof, all as will be illustratively described herein, andthe scope of the application of which will be indicated in the followingclaims.

In the accompanying drawings illustrating one of many possibleembodiments of the mechanical features of this invention,

Figure 1 is a cross sectional view taken along the axis of a moldconstructed in accordance with the invention and showing the retainingplates of a press which support the mold.

Figure 2 is another cross sectional view of the mold of Figure 1 on alarger scale.

.2 Figure 3 is a third axial sectional view of the interior of the moldon a further enlarged scale to show the construction in better detail.

The apparatus of the invention is used in an hydraulic press. The pressshould be capable of exerting a thrust of five hundred tons. Referringto Figure 1 the press, not shown, holds a plurality of superimposedsteel plates I!) having a continuous conical bore II extending there--through, whereby the plates encircle and reinforce a central cavityblock 12 which constitutes a mold. The thrust against the mold I2 isupward and as will be seen the mold l2 has a conical surface 13 whichfits the conical bore H, the lower end of the mold l2 and of the bore lI being of larger diameter than the upper end of the mold and the bore.Thus upward pressure on the mold l2 tends to drive it into the bore H sothat the reaction of the plates it exerts a compressive force radiallyinward of all parts of the mold l2.

We provide a specimen piston or ram i of small diameter, which exertsthe pressure in the mold l2. This piston or ram 15 may rest upon a blockl6 of some hard and strong material such as cemented tungsten carbide.An annular piece of steel [8 constitutes a retainer for .the block l6and prevents it from splitting. The retainer I8 is centered on the topof a ram head by means of a centering ring 2|. We may also provide acentering ring 22 for visually centering the piston or ram IE on theblock l6.

As shown, the ram head 20 is supported by a pair of semi-annular steelblocks 25 surrounding an auxiliary ram piston 26 to which the head 20 isremovably secured by means of a bolt 21. The auxiliary ram 26 is movablein a cylinder 29 in the main hydraulic ram 30. Upon the top of the mainhydraulic ram 30 is a removable ram head 3 I having a hole therethroughto receive the auxiliary ram 26. v

The foregoing construction is not per se our invention and may be variedwidely. The use of the auxiliary ram 25 and the semi-annular blocks 25,which are removable, makes itpossible to move the specimen piston or ram[5 through a comparatively long distance at low pressure and underaccurate control, and also rapidly. In other words, this is an expedientfor mold I2, and the large end of whichopens into a cylindrical chamber44 in which is located a cylindrical steel plug 45 abutting the screwplug 4|.

we provide a tapered anvil member 41 which fits the upper part of theconical bore 43 and extends part way into the cylindrical cavity 44. Wefurther provide a tapered mold liner 49, which fits the conical bore 43just below the anvil member 41. The anvil member 41 preferably has acylindrical projection 59 on the bottom thereof, which fits acounter-bore 5| at the top of the liner 49, thus to provide a good sealbetween these parts. The anvil member 41 and the mold liner 49 may bemade of steel, such as a good grade of tool steel. The liner 49 is in areal sense itself a mold.

Referring to Figures 1 and 2, the liner 49 has a cylindrical bore 52extending through it from end to end. The ram or piston l5 fits in thisbore 52, and on the upper end of the ram or piston 15, when it is in thebore 52, is a soft. steel sealing plate 53 having on its upper side aninteriorly tapered annular projection 54. Similarly, under thecylindrical projection 56 of theanvil member 41 is a soft steel sealingplate 56 having an interiorly tapered annular projection 51. The heatingcharge, the insulation and the specimen are placed in the chamber formedby the bore 52 and the sealing plates 53 and 56, and are thereinsubjected to pressure. The pressure is transmitted from the ram 30 viathe head 3i, the removable blocks 25, the head 20, the block 16 and thepiston to the sealing plate 53, then through the charge, insulation andspecimen to the sealing plate 56, thence to the anvil member 41, theplug 45, the screw plug 4| to the cavity block 12, which transmits thethrust to the plates lllwhich are held down by a massive iron cap 24which is a permanent part of the hydraulic press.

In accordance with the invention we provide a suitable heating charge,which will heat the specimen while it is under pressure, and we providesuitable means to ignite this charge. Desirably, we provide a detonator,an igniter and a main charge. We will describe the best combina ion nowknown to use, but it should be understood that other chemicals may beemployed so far as the broad aspects of the inyention are concerned. Asuitable detonator is tetracene. This is understood to have thefollowing structure:

NO N-CH:

Ha N01 N02 This detonator reacts upon impact and produces an intenseheat which ignites the igniter. As will hereinafter be described, weprovide means to set off the detonator upon the attainment of a certainpressure.

The igniter which we have successfully used is a combination of twomixtures. The mixture nearest the detonator was sugar and potassiumchlorate, KClOa, the sugar was sucrose. The sugar and the potassiumchlorate were mixed in stoichiometric proportions according to thereaction,

The second igniter mixture which was placed next to the first ignitermixture was magnesium and sodium peroxide. These were mixed instoichiometric proportions according to thereaction The proportion ofthe igniter mixtures was .080 part of the first and .350 part of thesecond. The main charge reacted according to the following formulae:

(1) Mg+Na2O2=MgO+Na2O (2) 3Mg+KClOs=3MgO+KCl However, stoichiometricproportions were not used, rather, the following proportions were foundto give good results:

P81 cent NazOz 19.1 KClOa 42.3 Mg 38.6

it being understood that the addition of MgO lowers the temperature.

Referring now to Figures 2 and 3, extending between the sealing plates53 and 56 was a cylindrical graphite casing 60 having a cylindricalchamber 6| opening to the upper side, the easing being bevelled atbottom and top to fit the annular projections 54 and 51. This graphitecasing 66 was of course crushable under the high pressure employed, butwould stay more or less in position and constituted refractoryinsulation. Inside and at the upper end of the graphite casing 60 was agraphite plug 62 having an axial bore 63. Plugging the upper end ofaxial bore 63 was a graphite plug 64. Under the graphite plug 64 was asteel plug 65 fitting the bore 63, the steel plug 65' having acylindrical projection 66 fitting a counterbore 61 in a steel container68, also fitting the bore 63. This steel container 68 had a taperedaxial bore 69, the large end being up, and the small end opening into awide cylindrical chamber 19 at the bottom of the container 66.

The tetracene in granular form is shown at 1| in the bore 69, not quitefilling the bore, but leaving an air space 12 above it. ,The bottom ofthe bore 69 was closed by a hardened steel disc 15 of a diameter thesame as that of the chamber 10, but of lesser thickness except for thecentral portion where an integral projection or button 16 fills thechamber 16. Under the container 68 and under the button 16 was a layerof powdered graphite 11 having the shape of ,a disc. Below the graphitelayer 11 was the first igniter mixture 18, also in the form of a disc.Under the first igniter mixture NaNs' or tetra nitro guanidine.

" ture 19, more or The mixtures "I8 and I9 were loose mixtures andtheboundaries were not exact, and some intermixture occurred.

Under the second igniter mixture 19 was a graphite container 80 havingan axial bore 8| opening at the bottom of the container 80. Under thecontainer 80 and blocking the bore 8| was a molybdenum disc 82. Thelower part of the steel container 68 plus the graphite I1 and themixture 18, the mixture 19 and'the graphite container 80 and themolybdenum disc 82, were all contained in a straight cylindrical bore 85in the main charge 86, which filled the bore 6| under the plug 62, allas clearly shown in the drawings, Figures 2 and 3. The main charge wasmolded and pressed to the shape shown, and had enough strength to holdtogether while being filled with the materials and parts described. Inthe bore 8| the-specimen 9|! was surrounded by powdered graphite 9| Thepurpose of the apparatus is to subject the specimen 90 to great heat andpressure simultaneously. Once the parts and mixtures are assembled asdescribed, the pressureis applied whenever the main ram 30 exerts thedesired thrust, which is accomplished by manipulation of the controls ofthe press, not shown. As soon as the pressure reaches a certain value,the charges are ignited and the specimen 90 is heated. This occurs inthe following manner.

The pressure between the sealing plates 53 and 56 compresses everythingbetween them, but the pressure on the button 16 is unsupported onthe-upper side due to the space 12. Finally, therefore, the disc 15shears and the button 16 shoots like a bullet into the tetracenedetonator ll. This sets off the detonator, whichfiashes back through thegraphite l1 and into the first igniter charge 18. This charge 18 ignitesand heats the main charge 86 and also sets ofi the second igniter charge19. The two charges.l8 and 19 together set off the main charge 86, whichprovides intense heat to the required temperature. This temperature ismaintained for a considerable time, due to the fact that it is developedentirely inside of an envelope of graphite. For that reason it does notmelt the steel parts. Gradually, of course, the heat is dissipated, butthe pressure can be maintained from the moment the tetracene is ignitedright through the heating cycle, and in fact for an indefinite period.

In practice the pressure has been maintained for usually about 5minutes, sometimes longer.

The detonator may be other than tetracene, the igniter may be difierentand the main charge may be different. For example, the detonator mightbe mercury fulminate, or sodium azide Many nitrated organic compoundsmight be used. A detonator should be sensitive and it should produce apowerful shock. We consider that picric acid is the borderline case withregard to sensitivity and our detonator should be at least as readilydetonated as picric acid. Explosive chemists can measure thesensitivityof detonators.

With regard to the shock producing properties we define our detonator asone which produces gas. By gas we mean anything which is a gas at justabove 100 C. 'or at 100 C. and somewhat less than 30'. of mercury. Wateris a gas under these conditions.

In some cases the igniter charge might be omitted and the main charge befired by the detonator. However for the most reliable results we preferto have an igniter and it will be noted that in the illustrativeembodiment of the invention a two stage igniter was provided.

It will be seen that the main charge comprises, and in fact in theillustrative embodiment mainly consists of, an elemental metal and'asubstance containing combined oxygen. In the illustrative embodimentmagnesium is the element and sodium peroxide and potassium chlorate arethe compounds containing oxygen. The elements magnesium, aluminum,lithium, calcium, strontium and barium have oxides which have a highheat of formation. The elemental metal which may be referred to as anelement should be selected from this group. The oxygen containingcompound'should be an oxidizing agent and may be defined as a compoundor compounds whose oxygen is as easily detached as the oxygen of ironoxide FeO. A mixture of aluminum and iron oxide when ignited gives ofiintense heat and is known as Thermite. It will be noticed that in theillustrative embodiment the reaction of the main charge does not producegas as above defined. It will be noticed on the other hand that one ofthe igniter mixtures reacts to produce gas. This is the mixture ofpotassium chlorate and sugar. The other or second igniter mixture isseen to be identical with one part of the main charge and from achemical standpoint may be considered as part thereof.

It has been pointed out that the plates l0 act as a reinforcement of thecavity block l2 due to the tapered outer surface of the latter and thethrust against it from the large end of the taper. The reverse taper ofthe bore of the cavity block permits the mold liner 49 and anvil member41, to be readily withdrawn from the cavity block l2 even after the raml5 has exerted an enormous thrust equivalent to 30,000 atmospheres ormore. We have ,found that a large screw plug 4| of the type shown anddescribed can be tightened sufliciently to hold the mold parts in placeunder these conditions of high pressure. One feature which permits thecavity block l2 to withstand the high tensile force is the comparativelylong dimension of the cavity block from the anvil member 61 to the plugAl.

The sealing plates 53 and 56 made of soft steel effectively confine thecharges and the specimen between them since the annular projections 54and 51 try to expand under the pressure. The taper of the bore 69 allowsthe button 16 to move like a bullet in the bore once the disc 15 hassheared oil. This insures detonation. The molybdenum disc 82 wasprovided as a check on the temperature reached and in many of theexperiments the molybdenum melted partially. Molybdenum has a meltingpoint of 2620 C. at ordinary pressures and we believe that the meltingpoint under these high pressures is not a great deal higher.

It will be seen from Figure 2 that the various charges and the specimenare all enclosed in graphite so that the heat persists for a reasonablylong time. Probably if the temperature at the time of reaction is 2700C. it does not drop below 2000 C. for a minute.

The apparatus and method of the invention can be used to studypolymorphism and for experiments in geophysical research. It can also beused to change the state of matter where that can be done with heat andpressure of the order indicated.

It will thus be seen that there has been provided by this invention amethod and an apparatus in which the various objects hereinabove setforth together with many thoroughly practical advantages aresuccessfully achieved. As many possible embodiments may be made of theabove invention and as many changes might be made in the embodimentabove set forth, it is to be understood that all matter hereinbefore setforth or shown in the accompanying drawings is to be interpreted asillustrative and not in a limiting sense.

We claim:

1. A mold for high pressure high temperatureattainment comprising};cavity block with an exterior conical surface and a conical bore, thetaper of the surface being opposite to that of the bore, means to plugthe bore at the large end, a liner fitting the bore and having acylindrical bore, a pair of sealing plates in said cylindrical bore,charges including a detonator and a main charge in said cylindrical borebetween said sealin plates, and a shearable element adjacent thedetonator which will fire it when great pressure is exerted between saidsealing plates.

2. Apparatus of the class described comprising a cavity block having anexterior conical surface and a conical bore, the taper of the surfacebeing opposite to that of the bore, there being a cylindrical bore inthe cavity block beyond the large the liner, whereby simultaneously toproduce high heat and pressure when said charge is ignited and said ramexerts pressure.

3. In apparatus claimed in claim 2, the combination with the parts andfeatures therein specified, of a detonating charge in the cavity blockand a shearable element to set oil the detonating charge responsive topressure exerted by the ram.

4. In apparatus of ,the class described, a mold liner having acylindrical bore, a pair of sealing plates in said bore, and in saidbore between said sealing plates the following: a detonating charge, ashearable element adjacent the detonating charge and so situated thatwhen it is sheared by pressure part of it will hit the detonatingcharge, and an exothermic charge, whereby pressure in said bore betweenthe sealing plates shears the element which sets off the detonatingcharge which sets off the exothermic charge thus heating a specimenwhich may have been placed between the sealing plates.

5. In apparatus for coincidentally heating a specimen and subjecting itto high pressure, a

mold having a bore, nieans blocking one end of the bore, a piston ramfitting the bore, a mass of refractory material in the bore said masshaving a cavity, and in the cavity the following: a shearable element, adetonating charge adjacent the shearable element in such position thatwhen the element is sheared part of it hits the detonating charge, anigniter charge adjacent the detonating charge, and a main exothermiccharge adjacent the igniter charge, whereby when the piston ram exertshigh pressure in the bore of the mold the element is sheared, thedetonating charge is set off, the igniter charge is set oif and theexothermic charge creates intense heat coincidentally with the pressurewhile the refractory material retards cooling.

6. 'In apparatus for coincidentally heating a specimen and subjecting itto high pressure, a.

mold having a bore, means blocking one end of the bore, a piston ramfitting the bore, and in the bore the following: a shearable element, adetonating charge adjacent the shearable element in such position thatwhen the element is sheared part of it hits the detonating charge, anigniter charge adjacent the detonating charge, and a main exothermiccharge adjacent the igniter charge, whereby when the piston ram exertshigh pressure in the bore of the'mold the element is sheared, thedetonatingcharge is set off, the igniter charge is set off and theexothermic charge creates intense heat coincidentally with the pressure.

PERCY W. BRIDGMAN.

SAMUEL S. KISTLER.

WILLIAM MAXWELL WHEILDON, JR.

REFERENCES CITED I The following references are of record in the file ofthis patent:

UNITED STATES PATENTS OTHER REFERENCES Jones: Inorganic Chemistry,Blakiston Co., 1947, p. 259. y

